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Publication numberUS4098856 A
Publication typeGrant
Application numberUS 05/831,992
Publication dateJul 4, 1978
Filing dateSep 9, 1977
Priority dateDec 29, 1975
Publication number05831992, 831992, US 4098856 A, US 4098856A, US-A-4098856, US4098856 A, US4098856A
InventorsClifford M. Rosenau
Original AssigneeArmstrong Cork Company
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method of making a composite mold for making polyurethane foam decorative parts
US 4098856 A
Abstract
A method for making a composite mold utilizing room temperature vulcanizing silicone rubber for the surface of the mold and room temperature vulcanizing polyurethane rubber for the rest of the mold.
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Claims(3)
What is claimed is:
1. A method of making a composite rubber mold comprising the steps of:
(a) spraying a silicone rubber compound on the surface of a master which is to be copied;
(b) curing the silicone rubber covering over the master to be copied to form a layer with a thickness of 0.005 to 0.020 inches;
(c) flame treating the back surface of the silicone rubber layer to make it receptive to bonding with other materials;
(d) forming a solid non-compressible during molding use flexible polyurethane backing layer on the silicone rubber surface; and
(e) permitting the composite plural layer mold to cure so that it may be subsequently used to mold articles in the shape of a master in the mold so constructed.
2. The molding method of claim 1 wherein the sprayable silicone rubber coating is placed over the master which is to be copied with areas of various thickness for the silicone rubber coating so formed.
3. The molding method of claim 1 wherein the silicone rubber compound is applied as plural coats.
Description
CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 644,752, filed Dec. 29, 1975 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a molding process and, more particularly, to a molding process for forming a mold which will subsequently produce articles for furniture.

2. Description of the Prior Art

The state of the prior art is fully spelled out in U.S. Pat. No. 3,883,627. That patent, in addition to describing the solid silicone rubber molds, describes a composite silicone rubber mold having a vacuum formed sheet silicone rubber surface and a foamed polymeric backing.

The method herein, through the use of a sprayable silicone rubber compound, will provide greater mold detail over that which can be secured from a vacuum formed sheet. A sprayable silicone rubber compound will permit a build-up of material at weak points of the mold contour to reinforce the silicone rubber surface at those points where it is subject to great stress. Finally, the use of a solid backing permits the composite mold to better simulate a solid silicone rubber mold. A foam backing, if rigid, would be difficult to use with undercut areas of the mold and, if made flexible to overcome this problem, then it would be compressible and result in problems holding tolerances in the finished furniture article.

SUMMARY OF THE INVENTION

A pattern is secured for making the silicone mold. A room temperature vulcanizing silicone rubber is made up in a sprayable form and sprayed upon the pattern. The silicone rubber is permitted to cure and the exposed surface of the silicone rubber is then flame treated. The exposed surface of the silicone rubber is then covered with a suitable polyurethane rubber to form the composite mold. The composite mold will have a silicone rubber surface with fine detail and a solid polyurethane rubber backing to give the mold the desired strength and flexibility.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As indicated in U.S. Pat. No. 3,883,627, the state of the art for making furniture molds is well known. Many different silicone rubber compounds are available for the purpose of making furniture molds. Molds will be made from silicone rubber and into the molds will be poured polyurethane, which will foam in the mold and form a rigid component which may be then placed upon a furniture unit. The invention herein is directed to a technique for making a mold adapted to form the foamed polyurethane furniture component.

A master or pattern of the furniture component to be formed is placed on a flat surface and an appropriate wall structure is formed therearound. This forms a mold cavity which will be used to make the composite mold which in turn will be the mold for forming the furniture component. The mold cavity with the master therein may be heated to about 180 to 200 F. to speed the cure of the silicone rubber which is to be subsequently applied. Generally any commercially available room temperature vulcanizing silicone liquid rubber compound may be used, and the compound is thinned by an appropriate solvent to a sprayable state. Silicone rubber compounds which can be used are Dow Silastic Q-38030 or General Electric RTV-664. These may be thinned to a sprayable consistency with a suitable solvent such as trichloroethylene, methyl ethyl ketone or toluene. Silicone rubber compounds are normally provided in two parts, and the two parts are mixed together just prior to use. The blended material is referred to as an activated silicone, and this is the material which is thinned to a sprayable consistency. The master and the inside parts of the mold cavity are sprayed with the sprayable silicone rubber to give a coating to the master and the mold cavity in the range of 0.005 to 0.020 of an inch in thickness. Certain areas of the mold being formed may have excessive wear or be subjected to excessive stress. These areas would be sprayed with extra silicone rubber to provide a thicker surface coating at those points. The coating of silicone rubber is then heated for about 2 hours at 150 F. to cure the coating. If desired, the silicone rubber spray coating could be placed on the master and the mold cavity as one spray coat or a plurality of spray coats, with gelling of the different spray coats between each application. Gelling can be carried out by heating the silicone for about 10 minutes at 275 F.

Normally, cured silicone rubber is a very difficult material to adhere to. Once the surface layer of silicone rubber has been placed over the master and the mold cavity and cured, the exposed surface of the silicone rubber is then subjected to a flame treatment which will now make that surface capable of adhering to the liquid polyurethane coating which will be cast on the back of the silicone rubber surface. Flame treatment consists of impinging momentarily the flame of a propane gas torch (or the equivalent) on the silicone surface to which other material is to be bonded. Care must be taken to assure that every area to be bonded is exposed to the flame.

After the flame treatment, a conventional liquid polyurethane casting material may be poured over the back of the silicone rubber surface layer to fill up the mold cavity and form a flexible backing bonded to the silicone rubber. A typical liquid polyurethane that may be used is Ren: C:O-Thane RP6401 made by Ren Plastics. This polyurethane is poured into the mold cavity over top of the sprayed-on silicone rubber coating, and the polyurethane is allowed to cure at ambient conditions for at least about two to three hours. The flame treatment has made it possible for the liquid polyurethane to bond to the silicone rubber. There has been formed a composite mold which has a solid polyurethane elastomer back with a silicone rubber mold surface. Into the now-formed mold one may pour foamable polyurethane to form furniture parts.

The composite mold above formed is similar in handling characteristics and size to conventional all-silicone rubber molds. The cast polyurethane foam furniture parts formed in the above composite mold will conform to the same dimensional standards as parts made in an all-silicone rubber mold and will have excellent grain detail due to the excellent grain detail on the silicone rubber surface of the mold. The material cost of the composite mold is approximately one-half that of an all-silicone rubber mold or less. The use of the liquid silicone rubber sprayed upon the master permits one to pick up the excellent grain detail from the master. A mold formed with sprayable silicone rubber may have the thickness of the silicone rubber surface varied, depending upon needs. Finally, while the composite mold is flexible to permit one to remove foamed polyurethane furniture parts from the mold, even furniture parts having undercuts, the mold backing is not compressed during the curing of the foamed polyrethane furniture part. If the backing of the composite mold were compressible, the pressure of the curing foamed polyurethane would compress the backing, and thus make it difficult to maintain tolerances.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2113166 *Jan 6, 1936Apr 5, 1938Woodall Industries IncMethod of making die patterns
US3030259 *Mar 1, 1956Apr 17, 1962Long Francis VintonMethod of fabricating precision formed plastic products
US3291882 *Nov 21, 1963Dec 13, 1966Polymer CorpMethod for producing thin-walled hollow polylactam articles
US3428725 *Dec 11, 1964Feb 18, 1969Furane PlasticsProcess of casting a polyurethane to form a flexible mold
US3883627 *Jun 6, 1973May 13, 1975Cook Paint & Varnish CoMolding process for producing subsequent articles from a master
US3900538 *Feb 13, 1973Aug 19, 1975Toray IndustriesMethod for surface treatment of plastics
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4589623 *Nov 5, 1984May 20, 1986Phoenix AktiengesellschaftMold for producing T-shaped rubber hoses
US4822549 *Jul 8, 1986Apr 18, 1989"Gechem"Method for preparing a shaped layer by gun spraying
US5207965 *Nov 20, 1991May 4, 1993Komine Rubber Industrial Co., Ltd.Dipping pattern mounted on plate; withdrawal, drying, vulcanization, and peeling
US5326521 *May 26, 1993Jul 5, 1994East Douglas AMixing, spraying and curing silicone rubbers
US5340512 *Jan 29, 1993Aug 23, 1994Thomas & Betts CorporationPolymer concrete electrical insulator and method and apparatus for making
US5380478 *Apr 28, 1994Jan 10, 1995East; Douglas A.Method for preparing silicone mold tooling
US5433165 *Mar 30, 1994Jul 18, 1995Outboard Marine CorporationMethod of manufacturing a boat hull
US5526767 *May 2, 1995Jun 18, 1996Outboard Marine CoporationMethod of manufacturing a boat hull
US5651924 *Nov 7, 1991Jul 29, 1997Tchai Lights B.V.Method for manufacturing light panels
US6290892 *Nov 29, 1999Sep 18, 2001Chung-Shan Institute Of Science & TechnologyProcess for preparing a laminated composite of addition type silicone rubber and polyurethane by induce surface reconstruction
US6358455 *Nov 29, 1999Mar 19, 2002Chung-Shan Institute Of Science & TechnologyProcess for preparing a laminated composite of condensation type silicone rubber and polyurethane by induce surface reconstruction
US6439874Dec 27, 1996Aug 27, 2002Leverbrothers Company, Division Of Conopco, Inc.Die especially for stamping detergent bars
US6994051Apr 8, 2002Feb 7, 2006Vec Industries, L.L.C.Boat and method for manufacturing using resin transfer molding
US7156043Nov 28, 2005Jan 2, 2007Vec Industries, L.L.C.Boat and method for manufacturing using resin transfer molding
US7373896Nov 21, 2006May 20, 2008Vec Industries, L.L.C.Boat and method for manufacturing using resin transfer molding
US7533626May 20, 2008May 19, 2009Vec Industries, L.L.C.Boat and method for manufacturing using resin transfer molding
US7785518Jan 18, 2008Aug 31, 2010Vec Industries, L.L.C.Method and apparatus for molding composite articles
US8672665May 19, 2008Mar 18, 2014Arjr Group, LlcVacuum bag with integral fluid transfer conduits and seals for resin transfer and other processes
EP0220154A1 *Jul 9, 1986Apr 29, 1987N.V. Gechem S.A.Method of making a shaped layer by spraying
EP0220898A2 *Oct 17, 1986May 6, 1987Komine Rubber Industrial Co., LtdMethod for manufacturing an elastic mould
EP2134523A1 *Feb 25, 2008Dec 23, 2009Richard W. RydinMethod of making and using a spray-formed natural rubber vacuum bag
WO1987000482A1 *Jul 8, 1986Jan 29, 1987Gechem NvMethod for preparing a shaped layer by gun spraying
WO1992008593A2 *Nov 7, 1991May 10, 1992Novem Optical Fibers BvA method and a device for manufacturing light panels
WO1996000278A1 *Jun 14, 1995Jan 4, 1996Unilever NvProcess for stamping detergent bars
WO1998029235A1 *Dec 19, 1997Jul 9, 1998Unilever PlcDie and process for stamping plastic material
WO2000000355A1 *Jun 23, 1999Jan 6, 2000Ge Bayer Silicones Gmbh & CoProduction of abrasion-resistant printed silicon shaped parts
WO2004091924A2 *Apr 7, 2004Oct 28, 2004Kampe Entpr LlcMethod of producing polyurethane surfaces
WO2008103485A1Feb 25, 2008Aug 28, 2008Richard W RydinMethod of making and using a spray-formed natural rubber vacuum bag
WO2012149179A1 *Apr 26, 2012Nov 1, 2012Aortech International PlcBonding process
Classifications
U.S. Classification264/80, 264/225, 249/134, 264/337
International ClassificationB29C33/40, B29C33/38, B29C35/18
Cooperative ClassificationB29C33/3857, B29K2875/00, B29C33/405, B29K2883/00, B29C35/18, B29C2033/3864
European ClassificationB29C33/38M2, B29C35/18, B29C33/40B